Piston for internal combustion engines



Sept. 13, 1932. F. eo'ssLAu PI$'1 ON FOR INTERNAL C6MBUSTION ENGINES F1194 Jan. 6. 1931 Patented Sept. 13, 1932 UNITED STATES PATENT OFFICE mrz eossLAu, or nnnrm-cmnor'rnnnune, GERMANY, Assmnon 'ro smumws a mum, AKTIENGESELLSCEAF'I, or SIEMENSSTAD'I, NEAR BERLIN, GERMANY, A

CORPORATION OF GERMANY PISTON FOB INTERNAL COMBUSTION-ENGIHES Application filed January 6, 1931, Serial No. 506,921, and in Germany August 10, .1929.

My invention relates to internal combustion engines, and more particularly to pistons for internal combustion engines.

The piston head of an internal combusition engine, for example of an aircraft motor, is, as is well known, a part of the engine particularly exposed to high temperatures. It has, therefore, already been suggested to provide a special liquid coolin for the piston .10 head. The danger of the piston head being excessively heated is ,thereby, no doubt, lessened but there is also the drawback that the liquid cooling is already efiective whenthe internal combustion engine is being started, .16 and counteracts in an undesirable manner the heating of the piston necessary'for the sure starting of the engine. p

It is also known to employ for cooling the iston-metals fusing easily and having melt- 1 mg. points down to 60 C. At the temperatures which the piston is in this case liable to assume, it is not possible to prevent an evaporation of the easily-fusing metals so that a considerable pressure is produced in the interior of the piston.

According to my invention these drawbacks are avoided by making at least the piston head of an, in itself already known, improvedv beryllium-alloy having a very high 80 heat conductivity. This has the eifect that, when the engine is being started, the piston becomes warm very quickly and thus facilitates the warming u Besides this, tosubsequently cool the plston, asubstance is em-- ployed, which is solid under ordinary conditions but changes, at aboutthe temperatu e the piston assumes when inoperation, into the liquid state without evaporating, and only produces a cooling efiect when this stage is reached. A salt or salt mixture melting at a sufliciently high temperature, for instance potassium nitrate and lithium nitrate known per se for similar purposes, may be used for cooling the piston head. As a rule, it is sufiiinto the piston, preferably in the form of powder, is about approximately 300 C... i

In the accompanying drawing an example is shown for carrying out the invention. In the piston body a the bore 6 is, as is known,

cient if the melting point of the salt, inserted provided to take the wrist pin. The piston rings are indicated at 6. Into the space between the piston head a and the wall d, a salt mixture f is introduced in powder form.

When a combustion motor provided with the illustrated piston is started the piston head ,0 becomes hot, as desire relatively quickly, as the salt f, which is at first still in the form of a solid mass due to the previous operation of the engine), oes not yet perform an independent movement'to and fro within the piston chamber, and does not, therefore, practically influence the heating in any way.

When during operation the temperature of the piston head o-has reached the melting point of the salt 7', the latter becomes liquid and effects by its splashing a vigorous coolingof the piston head a, by increasing considerably the transmission of heat from the piston head through the walls of the piston. The salt liquefied under the influence of the heat, washes, through the movement it mlakes, the inner side of the piston head and thereby carries away a greatpart of the heat from the piston head. Besides the piston head, other parts of the piston or the whole of thepiston may, if desired, be made of an improved beryllium-alloy.

Particularly suitable are copper-beryllium alloys containing up to 13% of beryllium. Suitable are also nickel-beryllium alloys, cohalt-beryllium alloys as well as iron-beryllium alloys. All the said alloys-may contain altogether, up to about 40% of additions of other metals, particularly copper, nickel, aluminum, magnesium, zinc, tin, phosphorus, silicon and carbon. Of the last three elements, in general, additions of only. a -fraction of a per cent come into consideration. Such beryllium alloys do not naturally possess any such properties as would make them appear particularly suitable for the present purpose. Through a suitable heat treatment, it is, however, possible to increase particular- 95 1y their hardness and mechanical strength to sucha high degree that they become an excellent material for the piston heador for the whole piston.

As a rule, it is advisable to make the piston 9 head, or the whole piston, of the desired beryllium alloi and thento improve the finished parts by su jecting them to a. suitable heat 1 treatment. Such a treatment may consist l substantially in cooling the parts quickly from temperatures between approximately 700 to 1200 0., according to the composition of the alloy in question, and in subsequently ageing them artificially at lower temperatures 10 between 250-500 C.

I claim as my invention:

1. In a piston for internal combustion engines having atleast its head made of a heat treated beryllium alloy, a normally solid 15 substance disposed adjacent to said piston head and adapted to liquefy at the normal operating temperatures of the piston and being non-vaporizable at said temperatures, for

transferring heat from the piston head of its sides.

2. In a piston for internal combustion engines having at least its head made of a heat treated beryllium alloy, a normally solid salt disposed adjacent to said piston head and adapted to liquefy at the normal'operating temperatures of the piston and being non-vaporizable at said temperatures, for transfer ring heat from the pistonhead to its sides.

3. A. piston for internal combustion engines having at least its head made of a heat treated beryllium alloy, and having a compartment adjacent to its head, partly filled with anormally solid substance adapted to liquefy at the normal operating temperatures of the piston and being .non-vaporizable. at said temperatures, for transferring heat from the piston head to its sides. 4. 'A' piston for internal combustion engines having at least its head made of a heat treated beryllium alloy, and having a compartmentadjaoent to its head, partly filled with a normally solid salt'adapted to liquefy at the normal operating temperatures of the piston and being non-vaporizable at saidtemperatures, for trgpsferring heat from the pistpn head toits si es. tnstimonywvhereof I aflix m signature.

' p i FRITZ SSLAU. 

